1. Field:
This invention relates to electrical contact assemblies for small light bulbs, such as miniature and sub-miniature bulbs used for computer console boards, automotive applications, displays etc., and more particularly to systems including a bulb to wire contactor that is amenable to assembly by high-speed automated or semi-automated production techniques.
2. Prior Art:
With the proliferation of devices requiring electrical connection such as wires in wire-to-wire assemblies, switches, light bulbs, integrated circuit chips, spark plugs etc., there continues to develop a demand for connectors and contactors that are especially adapted to meet requirements of economy, convenience and reliability. In the context of the art discussed here, "connector" means devices wherein electrical conductivity is a primary requirement such as wire-to-wire unions, chips to boards, switches etc., whereas "contactors" means devices wherein mechanical strength is a primary consideration and conductivity is secondary, needing only to be adequate for service requirements, such as bulb sockets.
The common requirement for all contactors is to maintain good electrical conductivity and mechanical strength that is not diminished by time or frequent separation and connection. Different purposes or uses demand different construction of the various contactors. For example a light bulb, comprising a fine filament supported within a glass envelope, must be mounted in a contactor that firmly supports the glass envelope and maintains sufficient electrical continuity between filament leads and two electrical source wire leads. The mechanical strength of the electrical contact must be sufficient to prevent intermittent contact under a variety of operating conditions (vibration, heat, cold, etc.) which could lead to flickering of the light or overheating that might cause a breakdown of insulation between the leads. Accordingly, the concept of the threaded plug and socket evolved whereby a sturdy male plug is screwed into an equally sturdy female receptacle so that the integrity of the glass seal and electrical continuity between filament and wire are maintained.
But with the development of display systems consisting of many light bulbs, the need is not only for an inexpensive contactor but also for a contactor that is amenable to assembly by automatic (production) techniques, and fast manual connect and disconnect which screw-in bulbs are not. The use of "receptacles on cords" for large numbers of lights, such as for Christmas trees, signs, displays and other light arrays, has stimulated a demand for a method of manufacturing electric cords having a large number of receptacles. Thus, a bulb contactor is required to provide continuous firm support to the bulb.
In contrast, the primary requirement for a wire-to-wire connector is to provide positive contacts and low resistance across the junction. There is also a need to reduce the size of wire to wire connectors since they are sometimes closely bunched or bundled in a manner not customary with light bulbs.
Wire-to-wire connectors are sometimes designed to withstand frequent connect and disconnect. Therefore, wire to wire connectors have been developed comprising a male and female part wherein each part has a ductile copper sleeve on one end adapted to enclosing the bare end of a wire and securing to the feed or live wire by a crimp. The engaging (mating) end is made of metal that is a compromise between the requirements for good resistance to breakage due to fatigue and good electrical conductivity. Copper beryllium is an alloy that is often selected for wire to wire connectors as being a good compromise of resiliency and conductivity, with just sufficient strength for the application.
U.S. Pat. No. 3,654,594 is an example of a wire-to-wire connector comprising a male and female spade-type termination part made of resilient metal, each of which is attached to a ductile metal crimpable barrel into which the bared feed wire is inserted and crimped. Assembly of the termination part to the crimpable barrel, and of the wire to the crimpable barrel is performed in two operations. In the first operation, a tab on the termination part is slipped into a retaining groove in the crimpable barrel part. In the second step, the wire is positioned onto the partially formed crimp barrel. The assembly is then punched in a crimping station so as to complete the closure of the crimp barrel and to secure termination, crimp barrel and wire together. Both terminators and crimp barrel are brought to the crimping station as attachments ("cut-outs") along a continuous ribbon.
U.S. Pat. No. 2,806,215 discloses a bi-metallic connector having one end crimped onto a wire and a ring for receiving a bolt at the other end.
U.S. Pat. No. 3,568,137 discloses a bi-metallic connector in which one end is designed for crimping to a wire of relatively small diameter while the second end is designed for crimping onto a wire having a larger diameter.
U.S. Pat. No. 3,320,574 discloses a bi-metallic device for connecting a wire to an electrical receptacle of the type having a receiving hole.
U.S. Pat. No. 4,209,221 discloses a two-piece socket terminal having a threaded socket for spark plugs on one end and a crimpable sleeve on the other end.
The above patents are carefully designed to meet critical requirements of very specific devices, e.g., spark plugs, wire-to-wire junctions, and the like.